Not applicable.
1. Field of the Invention
The present invention relates generally to disk drives, and in particular to a disk drive including disks having different disk stiffness, thickness and material combinations.
2. Description of the Prior Art
The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes the disk drive base, a cover, at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA).
The spindle motor includes a spindle motor hub that is rotatably attached to the disk drive base. The spindle motor hub has an outer hub flange that supports a lowermost one of the disks. Additional disks may be stacked and separated with annular disk spacers that are disposed about the spindle motor hub. The spindle motor typically includes a spindle motor base that is attached to the disk drive base. A shaft is coupled to the spindle motor base and the spindle motor hub surrounds the shaft. The spindle motor hub may be rotatably coupled to the shaft and therefore the spindle motor base typically via a pair of bearing sets. A stator is positioned about the shaft and is attached to the spindle motor base. A magnet element is attached to the hub flange. The stator includes windings that selectively conduct current to create a magnetic field that interacts with the various poles of the magnet element. Such interaction results in forces applied to the spindle motor hub that tend to rotate the spindle motor hub and the attached disks.
The head stack assembly has an actuator assembly having at least one head or slider, typically several, for reading and writing data to and from the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached sliders are moved relative to tracks disposed upon the disk.
The head stack assembly includes the actuator assembly and a flex circuit cable assembly that are attached to the actuator assembly. A conventional xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly typically comprises an actuator body, a pivot bearing cartridge, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms which that extend from an opposite side of the actuator body. The actuator body includes a bore and the pivot bearing cartridge engaged within the bore for allowing the actuator body to rotate between limited positions. At least one head gimbal assembly (xe2x80x9cHGAxe2x80x9d) is distally attached to each of the actuator arms. A head gimbal assembly includes a head for reading and writing data to and from the disks. In this regard, the actuator assembly is controllably rotated so as to move the heads relative to the disks for reading and writing operations with respect to the tracks contained on the disks.
It is contemplated that during operation of the disk drive, the inner disks may be subjected to different air flow conditions than the outermost disks, such as those adjacent the disk clamp and spindle motor hub flange. This is because the inner disks are disposed adjacent the other disks which are similarly rotating. Whereas the outermost disks are each disposed adjacent a similarly rotating structure (e.g., an innermost disk) and a respective stationary structure (e.g., the interior of the cover and the disk drive base among other disk drive components). Such differing air flow environments are contemplated to impact the motion of the disks differently. Comparatively, the inner disks are observed to have a higher degree of disk motion due to such air flow environment (i.e., disk flutter). Such disk flutter affects the position errors associated with positioning of the heads relative to the disks. In addition, it is contemplated that because the disks are repeating similarly configured structures in close proximity to each other, the disks may tend to become sources of resonance excitation to an adjacent disk resulting in relatively increased vibration amplitudes. Such relatively increased resonance amplitudes also impact to position errors associated with positioning of the heads relative to the disks. Accordingly, there is a need in the art for an improved disk drive in comparison to the prior art.
An aspect of the invention can be regarded as a disk drive that includes a disk drive base and a spindle motor hub rotatably coupled to the disk drive base. The disk drive further includes a first disk disposed about the spindle motor hub and having a first disk stiffness. The disk drive further includes a second disk disposed about the spindle motor hub and having a second disk stiffness different than the first disk stiffness.
According to various embodiments, the first disk may be an outermost disk and the second disk is an inner disk. The disk drive may further include a disk clamp, and the first disk may be disposed adjacent the disk clamp. The spindle motor hub may include a hub flange, and in another embodiment the first disk may be disposed adjacent the hub flange. The second disk stiffness may be greater than the first disk stiffness. The first disk may be formed of a material different than that of the second disk. For example, the first disk may be formed of a metallic substrate and the second disk may be formed of a glass substrate. The first or second disks may further be formed of a ceramic substrate. The first disk may have a thickness different than the second disk. Where the first disk is an outermost disk and the second disk is an inner disk, the second disk may have a thickness greater than the thickness of the first disk.
According to another aspect of the invention, there is provided a disk drive that includes a disk drive base and a spindle motor hub rotatably coupled to the disk drive base. The disk drive may further include a first disk disposed about the spindle motor hub and having a first disk thickness. The disk drive may further include a second disk disposed about the spindle motor hub and having a second disk thickness different than the first disk thickness.
According to various embodiments, the first disk may be an outermost disk and the second disk is an inner disk. The disk drive may further include a disk clamp, and the first disk may be disposed adjacent the disk clamp. The spindle motor hub may include a hub flange, and in another embodiment the first disk may be disposed adjacent the hub flange. The second disk thickness may be greater than the first disk thickness. The first disk has a first disk stiffness, and the second disk may have a second disk stiffness greater than the first disk stiffness. The first disk is formed of a first material having a first material stiffness, and the second disk may be formed of a second material having second material stiffness different than the first material stiffness. For example, the first disk is formed of a metallic substrate and the second disk is formed of a glass substrate. The first or second disks may further be formed of a ceramic substrate. In another embodiment, the first disk is formed of a material the same as the second disk.
According to another aspect of the invention, there is provided a disk drive that includes a disk drive base and a spindle motor hub rotatably coupled to the disk drive base. The disk drive may further include a first disk disposed about the spindle motor hub and formed of a first material having a first material stiffness. The disk drive may further include a second disk disposed about the spindle motor hub and formed of a second material having a second material stiffness different than the first material stiffness.
According to various embodiments, the first disk may be an outermost disk and the second disk is an inner disk. The disk drive may further include a disk clamp, and the first disk may be disposed adjacent the disk clamp. The spindle motor hub may include a hub flange, and in another embodiment the first disk may be disposed adjacent the hub flange. The first disk has a first disk thickness, and the second disk may have a second disk thickness the same of the first disk thickness. The first disk has a first disk stiffness, and the second disk may have a second disk stiffness is greater than the first disk stiffness. The first disk may be formed of a metallic substrate and the second disk may be formed of a glass substrate. The first or second disks may further be formed of a ceramic substrate. In another embodiment, the second disk may have a second disk stiffness substantially the same as the first disk stiffness.